Rao G N, Haseman J K, Grumbein S, Crawford D D, Eustis S L
National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina.
Toxicol Pathol. 1990;18(1 Pt 1):71-7. doi: 10.1177/019262339001800110.
Time trends for growth, body weight, survival and tumor prevalences in 121 diet control groups with a total of 4,636 male B6C3F1 mice and 123 diet control groups with a total of 4,758 female mice of NCI-NTP 2-yr chemical carcinogenicity studies started during a 9-yr period (1973 to 1981) in 11 laboratories were evaluated. Male and female mice did not show substantial changes in growth patterns. Both sexes had highly significant time trends with decreasing body weights in the more recent studies. This apparent trend was due to high body weights during the first 3 yr and highly significant interlaboratory variability. Time trends for survival of both sexes were not significant. Prevalences of liver tumors, lung tumors, and lymphoma in males and lung tumors in females did not show significant time trends. There were significant positive time trends for prevalences of liver tumors and lymphoma in female mice, but the trends were not significant when adjusted for interlaboratory variability. The positive time trend for anterior pituitary tumors of females was highly significant and may be due in part to an increase in the amount of pituitary tissue examined in the more recent studies. Histological reevaluation of liver and anterior pituitary tissue in 208-249 female mice at each of 4 different times periods did not substantially change the prevalences or the time trends. The major factor influencing time trends in mice appeared to be interlaboratory variability.
对11个实验室在9年期间（1973年至1981年）启动的NCI-NTP 2年化学致癌性研究中，121个饮食对照组（共4636只雄性B6C3F1小鼠）和123个饮食对照组（共4758只雌性小鼠）的生长、体重、存活率和肿瘤患病率的时间趋势进行了评估。雄性和雌性小鼠的生长模式没有显著变化。在最近的研究中，两性体重均呈高度显著的时间趋势下降。这种明显的趋势是由于前3年体重较高以及实验室间存在高度显著的变异性。两性的存活率时间趋势不显著。雄性的肝肿瘤、肺肿瘤和淋巴瘤以及雌性的肺肿瘤患病率均未显示出显著的时间趋势。雌性小鼠肝肿瘤和淋巴瘤的患病率呈显著的正时间趋势，但在调整实验室间变异性后，这些趋势并不显著。雌性垂体前叶肿瘤的正时间趋势非常显著，部分原因可能是在最近的研究中检查的垂体组织量增加。在4个不同时间段对208 - 249只雌性小鼠的肝脏和垂体前叶组织进行组织学重新评估，患病率和时间趋势没有实质性变化。影响小鼠时间趋势的主要因素似乎是实验室间的变异性。
